Late Nights, Life Lessons and Little Sister
by bananannabeth
Summary: When Sally and Paul have a daughter, Percy becomes the proudest, most overprotective big brother imaginable.
1. Ava's First Slumber Party

**a.n.** from a prompt sent to my tumblr ( **bananannabeth** ). more headcanons than fic but thought i'd share it here anyway.

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Percy is the proudest big brother ever. He brags to everyone, all the time. Annabeth and Grover are the only ones that can stand to listen to the non stop gushing.

He doesn't want to endanger his little sister, though, so he doesn't go to visit as often as he'd like to.

Sally and Paul make sure to keep him updated, still - They iris message every single weekend, and it becomes a game to see if he can surprise little Ava. Most of the time she's already there waiting for the call, jumping up and screaming either "Boo!" or "Percy!" as soon as he appears.

Sometimes it comes out as "Boocy!", a nickname which she takes a liking to. He gets referred to as "Big Brother Boocy" more often than he'd like, but he never says anything to her about it, because her smile makes the embarrassing name worth it.

When Percy and Annabeth do go to visit, Ava doesn't let them out of her sight. If she has to pee, Annabeth has to wait outside the bathroom for her, talking to her through the door the whole time so she knows she's still there. She holds onto Percy's hand, his sleeve, his leg, sits on his lap and fights for his attention constantly.

Annabeth convinces him that he should visit more often - that they'll be safe, especially if they stay around the apartment or make sure that the two of them are together whenever they take Ava out. He agrees, and when his visits become more regular Ava's clinginess dissipates somewhat. He kinda misses it.

When Annabeth hears that Sally and Paul have asked Percy to babysit, she reminds him that Ava loves her and she is head counsellor of the Athena cabin, so she is good at keeping children in line.  
"You talk to them like they're just mini adults, Annabeth."  
"You shouldn't talk down to children."  
"No, but - you know what, never mind. Just trust me, I've got this."

Percy makes dinosaur nuggets for dinner and chases Ava around the kitchen with a t-rex one before she triumphantly bites its head right off.

They build a giant blanket fort in the lounge and snuggle in to watch Finding Nemo. She asks him if he can speak whale and when he assures her that he can she makes an awful howling noise right in his ear.  
"What did I just say in whale?" she asks, giggling at how he winced.  
"You just said, _Percy is the best big brother in the world_."  
"No I didn't!"  
He pretends to think. " _My name's Ava and I'm a smelly little butt_?"  
"No! You're bad at this!"  
A new voice chimes in, "Did you say, _I wish Annabeth was here_?"  
Ava's whole face lights up and she rushes out of the blanket fort to tackle Annabeth in a hug. "Annabeth! I didn't know you spoke whale!"  
His girlfriend's smile is entirely too smug for Percy's liking, until she says sincerely, "Percy taught me some."

They put on The Little Mermaid next. Ava is asleep in Annabeth's lap by the time Part of Your World comes on, but they don't stop the movie. Percy dramatically sings the reprise - complete with hand gestures and longing stare - to Annabeth, who has to try and contain her laughter so she doesn't wake up his little sister.

As the credits roll they tuck her into bed, safe and sound, and return to the blanket fort.  
Annabeth nods approvingly. "This is well constructed. Bravo."  
"That's high praise." Percy smiles. "Thanks for coming round tonight."  
"Not gonna lie, I was a little worried about what I'd find."  
"What, you didn't think I could handle her?"  
"She can be pretty full on." Annabeth's smile is soft. "But of course I had nothing to worry about."  
"Of course." Percy beams and puffs his chest out proudly.

They sleep in the blanket fort that night, and are woken up by a very happy, very loud Ava at 6am sharp.

They make sure Sally and Paul don't miss out on the fun by cooking them breakfast in bed and serving it to them at 6.45.  
Sally reaches over her plate for their hands, smiling tenderly at the three of them. "We have the best kids in the world."


	2. Ava's First Boyfriend

Ava is 16 when she announces that she has a boyfriend.

Percy demands to know everything about him, and she rolls her eyes as she answers almost every one of his questions. His name is Liam, and he goes to school with her and he's on the basketball team and please could they not embarrass her when he comes over for dinner tomorrow night?

Percy makes no promises.

He tries to be polite to the kid, for Ava's sake. He smiles wide and shakes his hand and doesn't mention that he could kill him in a second if he ever hurts his little sister.

He asks about basketball and whether he plays any other sports. Liam plays soccer, just for fun, but he doesn't skateboard, which is a disappointment. He asks Percy if he plays any sports and Percy says, "I fence" which makes Annabeth snicker behind her hand.

Annabeth nudges his leg with hers under the table during dinner, nodding pointedly to where the young couple sit across from them. They're both grinning stupidly, which undoubtedly means they're holding hands under the table.

Sally's food is still delicious, of course, but Percy's too focused on Liam to really give it the attention it deserves.

When he walks in on the two of them leaning awfully close together on the couch while a soft pop ballad plays over the stereo, he clears his throat and puts on his most intimidating expression, glowering at the poor kid. Ava goes bright red.

Annabeth is more understanding. She likes Liam, because he's interested in engineering and so they have a small sample of common ground to cover. He seems genuinely interested about her job as an architect. When he asks her if he'd know any of the buildings she's designed, Percy says, "The Empire State Building."  
She shoots him a look and clarifies, "Renovations."

Percy softens when Liam looks suitably impressed.

Annabeth corners Percy in the hallway, splaying her hands on his chest. "What do you think?"  
"I don't like it." He pouts.  
"You don't like him, or you don't like Ava dating?"  
"The second one."  
"We were that age when we started going out."  
"I know, that's why I'm worried."  
Annabeth frowns. "Why does that worry you?"  
"I was lucky," Percy clarifies. "How many people start dating the love of their life at 16? What if he breaks her heart?"  
"We deal with it if it happens," Annabeth says reasonably.  
He sighs and runs his hand down his face. "I could show him Riptide. You know, just to get the point across."  
"Nice pun, but all he'd see is a pen, or a baseball bat or something mundane."  
Percy pulls Riptide from his pocket and uncaps it, the blade glinting in the dim light. "Baseball bat could still work."

A gasp from the end of the hall makes them tense. Annabeth immediately steps in front of Percy and he quickly puts the cap back on Riptide, shoving the pen into his pocket.

Ava is glaring at him, but Liam looks positively stunned. He points at Percy and asks, "Why do you have a sword? And did you just put it in your pocket?"

They all turn to gape at him, Ava included. "Oh, gods."


End file.
